Quote from: guckyfan on 12/06/2013 05:51 pmQuote from: meekGee on 12/06/2013 05:45 pmhow long does it take to cradle, tilt, and untilt IYO?They have to cradle it somehow for moving, no matter moving horizontal or vertical.Their declared aim is to go from hangar to launch in one hour. But that seems hard as it includes tanking and the whole launch sequence. But tilting horizontal and back should be less than that. I don't see them moving the vertical stage in that time by even only a few hundred meters.I think if it can land on its legs, it can be towed on its legs. You need to attach a dolly to each one, just like they do to skidded helicopters, but that's much simpler than attaching a cradle to an empty unpressurized tank.It's not a fragile process, there's no alignment necessary etc. Just one dolly at a time, it can be done pretty much manually by the tow-tractor driver. The tractor can then move at least as fast as the one pushing your plane back at the airport, which is a good walking speed, and so 3-5 km/h. If you're 1 km away, you're done in 10-20 minutes. (and honestly I think you can drive faster...)If you want to get fancier, you can invest in motorized, individually controlled dollies, and no tractor.
Quote from: meekGee on 12/06/2013 05:45 pmhow long does it take to cradle, tilt, and untilt IYO?They have to cradle it somehow for moving, no matter moving horizontal or vertical.Their declared aim is to go from hangar to launch in one hour. But that seems hard as it includes tanking and the whole launch sequence. But tilting horizontal and back should be less than that. I don't see them moving the vertical stage in that time by even only a few hundred meters.
how long does it take to cradle, tilt, and untilt IYO?
Moving something as tall as a rocket in a vertical position will probably present more problems than it is worth. The height of the rocket would make moving it under things like bridges or anything else in the way difficult. The height could elevate the center of gravity making it tippy. The height could be acted on by high winds attempting to push it down. Fluids that need to be drained before moving could be drained while the rocket is vertical and other fluid systems could be designed to stay in the tank when tilted over.The rocket isn’t going to need to be turned around in minutes or hours like a car, race car, or airplane and working on it in an horizontal position gives lots of advantages ( safety for personal since they don’t need to climb on something or be in danger of dropping tools as much—i.e. most of the work being done on the ground.) and the rocket is already built to be worked on in an horizontal fashion. The second stage is likewise currently built and matted on the ground. About the only reason why rockets in the past used vertical integration was for performance reasons (i.e. design the thing to take loads in one direction only saving weight…even if adding processing costs).
The premise was rapid reuse. 1-day turn-around or thereabouts.
We have seen SpaceX do the lowering and raising of the LV pretty quickly in the past. Once horizontal it can be rotated for easy access. Integrating the current F9 vertically would require some very complex and tall structures and from what I understand, this problem is not going to get smaller with their future vehicles.Complex and tall buildings are expensive.I can see vertical integration only to make sense if the VTOL LV has a much larger diameter to length ratio, like say a DC-X or a Phoenix and is not quite as tall, or if the LV launches pretty much from where it landed and is a VTOL SSTO (which probably would have a large diameter to length ratio anyway). Then going horizontal becomes a lot less useful and much more complicated.Current SpaceX vehicles both active and planned (that I know of anyway), are not like that. So the only justification seems to be customer request.
Which vehicle are you referring to?I know of F9 and F9H, and all we know of them is that SpaceX intends to reuse cores with them - eventually. Very far from rapid reuse.There isn't a current market for rapid reuse, and as I said, Elon is too smart to jump into expensive infrastructure for a market that does not exist. The current mode of operations is perfectly suitable for the current and the near-term projected launch rate.
Quote from: meekGee on 12/06/2013 06:50 pmWhich vehicle are you referring to?I know of F9 and F9H, and all we know of them is that SpaceX intends to reuse cores with them - eventually. Very far from rapid reuse.There isn't a current market for rapid reuse, and as I said, Elon is too smart to jump into expensive infrastructure for a market that does not exist. The current mode of operations is perfectly suitable for the current and the near-term projected launch rate.Ok, either you did not understand my post, or I don't understand what you are trying to say.
Current SpaceX vehicles both active and planned (that I know of anyway), are not like that. So the only justification seems to be customer request.
The premise was rapid reuse. 1-day turn-around or thereabouts.I agree there's no point making any changes when you're only launching once a month.The tail of a 747 is 65 feet, and you don't worry about it striking power lines or bridges between the terminal and the runway, right? We're talking about a recurring operation here, not a one time exercise.Center of gravity of an empty first stage - how high do you think that is? I don't see why you'd have any problem with it, though I'd like to see the F9R with legs deployed first.
I actually see almost no difference in processing between a VTOL SSTO and a VTOL first stage - up until the payload - but like I said before, payload integration is really a separate issue.
Quote from: meekGee on 12/06/2013 07:14 pmI actually see almost no difference in processing between a VTOL SSTO and a VTOL first stage - up until the payload - but like I said before, payload integration is really a separate issue.There is a difference. A VTOL SSTO might not need to have an 2nd stage hoisted over it an VTOL first stage(unless it works in parrell, will) as well as the payload and fairings.
But I guess you meant "like that" as in "like a wide diameter SSTO".
I mean, I know that looks can be deceiving, but to me the SpaceX way looks cheaper and more efficient than the Atlas way:http://www.spacex.com/sites/spacex/files/styles/media_gallery_large/public/img_2181_0.jpg?itok=G5EMKxrMversus:http://www.americaspace.com/wp-content/uploads/2013/11/MAVEN-Atlas-2.jpg
Spacex can't fly many types of payloads with its method. The Atlas method was driven by USAF requirements. Also, Spacex can't adapt their launch vehicle to increasing spacecraft performance requirements.
Quote from: Elmar Moelzer on 12/06/2013 08:00 pmI mean, I know that looks can be deceiving, but to me the SpaceX way looks cheaper and more efficient than the Atlas way:http://www.spacex.com/sites/spacex/files/styles/media_gallery_large/public/img_2181_0.jpg?itok=G5EMKxrMversus:http://www.americaspace.com/wp-content/uploads/2013/11/MAVEN-Atlas-2.jpgActually, I really liked these two pictures since they illustrate the point well. Obviously the service tower looks "more expensive".But compare these two pictures.Obviously the first picture looks "more expensive". But we know that with enough volume, the investment in that infrastructure pays off, and the actual per-unit costs are lower.Rockets are not sold by the millions, but the comparison is still valid. When you want to turn around rockets in a day, you need something much more like the Atlas facility then like the SpaceX facility. I think the vertical facility is the "industrialized" way of doing things, and the SpaceX way, right now, is more like the second picture.
A vertical rocket gives you access to everything at once. All 9 engines, in vertical position, the bells can be centered and unloaded, all vertical walls are accessible at eye level simply by walking to them, all fluid tanks and plumbing only ever see one orientation, so draining and such is easier (trap-wise), etc.A horizontal rocket only gives you sort-of-good access to the lower engine, and you have to rotate it. So if you're servicing engine #3 and need to escalate something for deeper inspection, all the other teams (e.g working on the RCS thrusters) have to wait since the rocket can't roll. (not to mention that access to the center engine is awkward)
